Intermolecular Compounds Research Articles

Solid-state green synthesis of two (1:1) organic intermolecular compounds; their physico-chemical, thermal, single crystal growth, and atomic packing studies

The solid-state solvent free reaction method has been adopted for the one-pot synthesis of novel organic materials with utmost 100 % yield. To identify the composition forming the intermolecular compound (IMC), the solid-liquid equilibria of entire compositions have been studied by establishing the phase diagram of n, n-dimethylaminobenzaldehyde (DMAB) with anthranilamide (AN) and 2-chloro-4-nitro benzoic acid (CNBA). The structural changes and novelty of the IMCs to that of parents are studied using FTIR, NMR and X-ray diffraction. The studies of optical properties of intermolecular compounds using UV–vis absorption and fluorescence spectroscopy infer the significant fluorescence emission. The single crystals of both intermolecular compounds, ANDMAB and DMABCNBA, are grown from solution using slow evaporation technique. The single crystal X-ray diffraction studies reveal that IMC of AN and DMAB is a racemic mixture whereas IMC of DMAB and CNBA is a co-crystal, and both the crystals have crystallized in triclinic P1‾ space group. The thermal stability and thermal behaviors are also studied using the experimental heat of fusion values obtained from differential scanning calorimetry (DSC).

ИЗУЧЕНИЕ ПРОЦЕССОВ КОМПЛЕКСООБРАЗОВАНИЯ В ПОЛИМЕРНЫХ БИОДЕГРАДИРУЕМЫХ КОМПОЗИЦИЯХ

One of the possible directions of the development of targeted substance delivery systems is the creation and introduction of biodegradable polymers into production. Their distinctive feature is that they are capable of spontaneously gradually degradation in the body due to natural biochemical processes. There is an increasing spread pharmaceutical form, which use similar excipients in their technology – medicinal ocular insert. Modified cellulose, gums and rare-cross-linked acrylic polymers are used to create a biodegradable matrix base. In terms of development approach, ocular inserts can be divided into two groups according to the principle of matrix biodegradation. In non-biodegradable composites, the effect of prolongation of the therapeutic effect is observed due to the release of the active substance from the non-decomposing matrix. This fact can be confirmed by both pharmacopoeial and non-pharmacopoeial methods. The classic tests regulated by the Pharmacopoeia of the XV edition include the "Dissolution" test (GPM.1.4.2.0014 "Dissolution of solid pharmaceutical dose forms"), and for non–pharmacopoeial ones – dialysis through a semipermeable membrane according to Kruvchinsky or using Franz's dialysis cells. The analysis of the kinetics of dissolution helps to determine and select the most suitable matrix-forming agent to be used in the composition with other substances in the composition of ocular insert. Ocular inserts with a biodegradable matrix have a second factor that affects the release of active substances – the formation of complexes or associates between parts of the matrix and the active ingredient molecules. These intermolecular compounds can indirectly prolong the effect of the drug. All features must be taken into account in the development of ocular inserts, since they, among other things, help to model fundamentally new ways of targeted delivery of substances. In this case, it is necessary to develop a test for the second modified release factor, which would reliably determine the presence of complexation processes within the selected ocular inserts model.

Solid-Liquid Equilibrium Study for Binary System Forming Intermolecular Compound: Phase Diagram, Thermal, Physicochemical and Powder XRD study

The phase diagram study of the binary organic system has been investigated by the thaw melt method using 4-hydroxy- 3 methoxybenzaldehyde (HMB) and 4-nitroaniline (NA). The temperature-composition plot showed that the intermolecular compound (IMC) has formed at 1:1 molar ratio with two eutectics on either side of IMC. The melting points of eutectics and IMC along with parents are verified by the DSC method. The different phases of the systems which are in equilibrium and their physicochemical properties are estimated using the enthalpy of fusion values obtained from DSC. The higher melting temperature of IMC suggested the formation of Schiff base during homogenization process. The new and moderately sharp Bragg’s peaks at specific 2θ values found in the diffractogram of IMC revealed the novelty and crystalline nature of IMC while repeated peaks in the diffractogram of eutectics suggest the mechanical mixture of eutectics

Green synthesis, characterization and optical properties of eutectics and 1:1 intermolecular compounds: N,N-dimethylaminobenzaldehyde–anthranilic acid and 2-(4-(dimethylamino)benzylideneamino)benzoic acid–p-nitroaniline systems

Phase diagrams of N, N-dimethylaminobenzaldehyde (DMAB)–anthranilic acid (AA) and 2-(4-(dimethylamino)benzylideneamino)benzoic acid (DMABAB)–p-nitroaniline (PNA) systems, determined by the thaw-melt method, give two eutectics and a 1:1 intermolecular compound (IMC) in each case. Appropriate amounts (10 g) of each of the eutectics and the IMCs were prepared by a green synthetic method involving a solid state reaction without any solvent. These materials were characterized by X-ray diffraction, thermal and spectral methods and the optical properties of the pure components and the IMCs were studied. While negative values of heat of mixing in the case of a DMAB–AA system suggest clustering of molecules in both eutectic melts, those of positive value in \(\hbox {E}_{1}\) and negative value in \(\hbox {E}_{2}\) of the DMABAB–PNA system indicate the formation of a quasi-eutectic structure in \(\hbox {E}_{1}\) melt and clustering of molecules in \(\hbox {E}_{2}\) melt. The IMC of DMAB–AA system shows strong dual emission with two \(\lambda _{\mathrm{max}} \) one at 380 nm and the second at 450 nm with a total quantum efficiency of 0.49. The IMC of DMABAB–PNA system also shows a similar observation with two \(\lambda _{\mathrm{max}} \) one at 390 nm and second at 435 nm with a total quantum efficiency of 0.31.

Crystal growth and some physicochemical studies on an organic intermolecular compound of anthranilic acid and N,N-dimethylamino benzaldehyde

The phase diagram of anthranilic acid and N,N-dimethylaminobenzaldehyde system gives two eutectics (E1 and E2) and a 1:1 intermolecular compound with congruent melting point. The mole fractions of anthranilic acid at E1 and E2 are 0.10 and 0.95, respectively. The negative values of heat of mixing of eutectics suggest that there is clustering of molecules in their eutectic liquid melt. The positive values of excess free energy for eutectics indicate that the interactions between the like molecules are stronger than those of unlike molecules. It can be inferred from single crystal X-ray analysis of the intermolecular compound that it crystallized in monoclinic unit cell with C2/c space group and a reasonably large sized intermolecular compound crystal was grown by slow evaporation technique at room temperature. The optical studies on the intermolecular compound give two strong emission bands with two lmax values one at 380 nm and second at 450 nm with total quantum efficiency 0.49.

Solvent free synthesis of a novel intermolecular compound and its crystal structure, thermal and optical studies

Novel intermolecular compound (IMC) of anthranilic acid and dinitrobenzene has synthesized by solvent free synthesis and its large size single crystal has grown using solution growth technique and mixed solvent. The stoichiometry of the IMC was determined by phase diagram study. The spectral, single crystal XRD and atomic packing studies of the IMC confirmed the hydrogen bonding association between the parent compounds. The DSC of IMC showed a sharp melting peak at 141 °C, however TGA study confirms its thermal stability up to 220 °C. The solvent effects on the electronic absorption and fluorescence spectra of IMC have been studied as function of solvent polarity and their quantum yields are calculated in different solvents. The optical transmittance spectrum of as grown crystal of IMC shows 55% transparency however its energy band gap and refractive index are found to be 3.40 eV and 2.29, respectively.

Green synthesis, crystal growth, and some physicochemical studies on an inter-molecular compound of anthranilic acid and m-nitro-benzoic acid system

The phase diagram of anthranilic acid (AA)–m-nitro benzoic acid (NBA) system, determined by the thaw–melt method, shows the formation of a 2:1 (AA:NBA) inter-molecular compound (IMC) and two eutectics E1 and E2 containing 0.084 and 0.917 mol fractions of AA, respectively, with one eutectic on either side of the IMC. The heat of mixing, entropy of fusion, roughness parameter, interfacial energy, and the excess thermodynamic functions were calculated from the enthalpy of fusion data, obtained by the DSC method. While the spectroscopic investigations (IR and NMR) and optical studies suggest the presence of hydrogen bonding between the components, the powder X-ray diffraction spectra of eutectics and the IMC suggest that the eutectic E1 is a mechanical mixture of the IMC and NBA and the eutectic E2 is a mechanical mixture of the IMC and AA. A single crystal of cocrystal of AA and NBA was grown using slow evaporation technique at room temperature from its saturated solution in methanol solvent. Single-crystal analysis of the grown cocrystal shows the mode of the intermolecular hydrogen bonding in the molecule and the triclinic crystal structure with P − 1 space group.

The Strength of Hydrogen Bonds between Fluoro-Organics and Alcohols, a Theoretical Study.

Fluorinated organic compounds are ubiquitous in the pharmaceutical and agricultural industries. To better discern the mode of action of these compounds, it is critical to understand the strengths of hydrogen bonds involving fluorine. There are only a few published examples of the strengths of these bonds. This study provides a high level ab initio study of inter- and intramolecular hydrogen bonds between RF and R'OH, where R and R' are aryl, vinyl, alkyl, and cycloalkyl. Intermolecular binding energies average near 5 kcal/mol, while intramolecular binding energies average about 3 kcal/mol. Inclusion of zero-point energies and applying a counterpoise correction lessen the difference. In both series, modest increases in binding energies are seen with increased acidity of R'OH and increased electron donation of R in RF. In the intramolecular compounds, binding energy increases with the rigidity of the F-(C) n-OH ring. Inclusion of free energy corrections at 298 K results in exoergic binding energies for the intramolecular compounds and endoergic binding energies for the intermolecular compounds. Parameters such as bond lengths, vibrational frequencies, and atomic populations are consistent with formation of a hydrogen bond and with slightly stronger binding in the intermolecular cases over the intramolecular cases. However, these parameters correlated poorly with binding energies.

Thermal, physicochemical and spectroscopic studies on some novel organic complexes obtained by green synthesis

The solid–liquid equilibrium phase diagram and thermochemical studies on two binary organic systems involving N-methylurea (MU) with 4-nitrophenol (NP) and 3-nitrobenzoic acid NBA were studied. Both systems show the formation of an equimolar intermolecular compound (IMC) and two eutectics (E1 and E2) one on either side of the IMC. Thermodynamic parameters such as heat of mixing, entropy of fusion, roughness parameter, interfacial energy and excess thermodynamic functions of intermolecular compounds and eutectics were calculated using the experimentally determined enthalpy of fusion by the DSC method. The spectroscopic studies, FTIR and NMR, of both the IMCs along with their parent compounds revealed the hydrogen bonding association between the parent moieties forming the complex. The findings were also confirmed by the appearance of new peaks in the powder XRD of the complexes in addition to their parent compounds.

Synthesis and studies on structural, optical and nonlinear optical properties of novel organic inter-molecular compounds: 4-chloro-3-nitroaniline−3-hydroxy benzaldehyde and urea−4-dimethylaminopyridine

Two novel organic inter-molecular compounds (IMCs), (3-(4-chloro-3-nitrophenylimino) methyl) phenol) (CNMP) and urea ̶ 4-dimethylaminopyridine complex (UDMAP), have been synthesized by solid state reaction. These two IMCs were identified by phase diagram study of CNA−HB and U−DMAP systems. The single crystals of newly obtained IMCs were grown by slow solvent evaporation technique at room temperature. Both the IMCs were further studied for their thermal, spectral, single crystal XRD for their atomic packing in molecule, crystallinity, optical and nonlinear optical behaviour. In both the cases, melting point of inter-molecular compounds was found to be higher than that of their parent components, CNMP was found to be thermally stable up to 158 °C while UDMAP was stable up to 144 °C, which indicate their extra stability than their parents. The single crystal XRD studies confirmed that CNMP has crystallized in orthorhombic unit cell with non-centrosymmetric space group P212121 while UDMAP has crystallized in monoclinic unit cell with centrosymmetric space group C2/c. The absorption spectrum of CNMP was found to be in between the absorption of parents, while broadening of peak and red shift was observed in UDMAP as compared to the parents. Second order nonlinear optical property of CNMP and UDMAP was studied using Kurtz Perry powder technique and intense green light emission was observed with CNMP on excitation with 1064 nm of Nd:YAG laser while no emission was observed with UDMAP.

Reversible Formation of an Inter-Molecular Compound Comprising 3ʹ-Aminofluorene-9-spiro-5ʹ-imidazolidine-2ʹ,4ʹ-dithione and Benzene

Reversible Formation of an Inter-Molecular Compound Comprising 3ʹ-Aminofluorene-9-spiro-5ʹ-imidazolidine-2ʹ,4ʹ-dithione and Benzene

Experimental Studies on Thermo-Mechanical Behavior of Ultrasonically Welded PC/ABS Polymer Blends

This research paper attempts to investigate the performance of blended PC/ABS joints using the ultrasonic material joining process. The key focus is on examining the thermal aspects during the joining of PC/ABS blends using ultrasonic welding and the subsequent mechanical testing to determine the strength of the weldments. Thermal behavior of the blends during welding may govern or alter the mechanical properties and integrity of the joints. Hence, investigations on thermal characteristics involved in PC/ABS blends when subjected to high vibrational heat generated during the ultrasonic welding process is imperative. DSC is used to measure the glass transient temperature (Tg) after subjecting it to welding. Mass loss is calculated with TGA. TGA and DSC results indicate change in Tg which are attributed to the molecular alignment occurring when the specimens are subjected to ultrasonic vibrations. Initially, two step mass losses occur that is contributed by ABS in which long single chains are associated and alters PC. SEM images reveal the absence in intermolecular compounds or impurities that tend to weaken weld joints. The diffusion of these molecules is uniform in the welded region. The amorphous nature enhances the integrity of weld joints. Molded part illustrates the higher strain rate in comparison with the welded specimens. The RSM model proposed is sufficient and has limited possibility for violating the independence or the assumption of constant variance.

Green synthesis, characterization and some physicochemical studies on cocrystal; 2-(4-(Dimethylamino) benzylideneamino) benzoic acid and p-nitroaniline system

Phase diagram of 2-(4-(Dimethylamino) benzylideneamino) benzoic acid (DMABAB) and p-Nitro aniline (PNA) system, determined by the thaw-melt method gives two eutectics and an inter-molecular compound (IMC)/cocrystal with congruent melting point. It was structurally characterized by X-ray crystallography methods. The cocrystal shows synthonic interactions with NH⋯O bridge to the centroid of an adjacent molecule. The synthon also shows interesting NH⋯C and H (N)⋯O interactions. It was noted to emit significantly high dual fluorescence with large Stokes shift and high quantum efficiency. Measurement of the solubility of the cocrystal was studied in the range from 300 to 315K. Reasonably large sized cocrystal was grown by slow evaporation technique and optical band gap and refractive index were also calculated with the help of transmittance spectra. Some physicochemical properties (enthalpy of dissolution, entropy of dissolution and enthalpy of mixing) of cocrystal were also estimated with the help of solubility data.

Solid state synthesis, structural, physicochemical and optical properties of an inter-molecular compound: 2-hydroxy-1, 2-diphenylethanone-4-nitro-o-phenylenediamine system

The phase diagram of 2-hydroxy-1, 2-diphenylethanone (HDPE)-4-nitro-o-phenylenediamine (NOPDA) system, determined by the thaw-melt method, gives two eutectics E1 (m p = 66.0°C) and E2 (m p = 155.0°C) with 0.30 and 0.55mol fractions of NOPDA, respectively, and an 1:1 inter-molecular compound (IMC) (m p 162.0°C). This IMC was synthesized by adopting the green synthetic method of solid state reaction. While its formation and structure were confirmed by the X-ray diffraction and spectroscopic methods, the ORTEP view gives mode of crystal packing, C‒H…O, C‒H…N, π-π stacking and the inter-molecular hydrogen bonding in the compound. The single crystal of the IMC shows 53% transmission and emits significantly higher dual fluorescence, and the band gap was computed to be 3.04eV. The values of solubility of the IMC, measured in the temperature range 304–322K, satisfy the mole fraction (X) and temperature equation: Xeq= 5.1324 × 10−7 e 0.01356T.

Some physicochemical studies on organic eutectics and inter-molecular compounds

Phase diagrams of o-phenylenediamine (OPDA)–N,N-dimethylaminobenzaldehyde (DMAB) and salicylamide (SAM)–m-nitro benzoic acid (NBA) systems, determined by the thaw-melt method, show the formation of two eutectics and one inter-molecular compound (IMC) in each case. These inter-molecular compounds were synthesized by the solvent-free method involving thermally initiated molten state reactions. Their characterization by the IR and the 1H NMR techniques suggest the formation of a new compound. Absorption spectrum of IMC of OPDA–DMAB system shows band at 245 nm due to the π → π* transition and another broad band observed from 280 to 440 nm is attributed to the n → π* transition. Their IMC shows fluorescence at 388 nm with a Stokes shift (93 nm) and quantum efficiency (0.0032) upon excitation at 350 nm in ethyl alcohol. Emission and absorption were observed in case of SAM–NBA system too. While the values of enthalpy and entropy of fusion of inter-molecular compound in case of OPDA–DMAB are 23.58 kJ mol−1 and 57.20 J mol−1, respectively, in the case of SAM–NBA system the corresponding values are 69.50 kJ mol−1 and 170.00 J mol−1. The values of interfacial energy in case of OPDA–DMAB and SAM–NBA inter-molecular compounds are 37.84 × 10−3 and 40.39 × 10−3 J m−2, respectively.

Green synthesis, characterization and some physico-chemical studies on a novel intermolecular compound; 4-nitro-o-phenylenediamine−N, N-dimethylaminobenzaldehyde system

An inter-molecular compound (IMC) L1 was synthesized by taking 1:1 molar ratio of p-nitro-o-phenylenediamine (NOPDA) and N, N-dimethylaminobenzaldehyde (DMAB) via thermally initiated solid state reaction. It was characterized by X-ray diffraction, spectral and optical studies. The single crystal of the (L1) was grown from saturated solution of ethanol using slow evaporation technique at 29 °C. From the single crystal X-ray diffraction analysis, it can be inferred that it crystallizes in triclinic unit cell with P-1 space group (CCDC No 1422765). Absorption spectrum of IMC (L1) shows a band at 318 nm attributed to the intra-molecular charge-transfer (ICT) excited state absorption and the other band at 376 nm is due to n→π* transition. The IMC (L1) shows a strong fluorescence at 418 nm with a Stokes shift (≈100 nm) and quantum efficiency (0.22) upon excitation in methyl alcohol at 318 nm.

Remarkable dielectric properties of 1 : 2 inter-molecular compound of 2-(4-(dimethylamino) benzylideneamino) benzoic acid and urea due to excited-state intramolecular proton transfer

The phase diagram of DMABAB–U gives two eutectics E1 (107.0 °C) and E2 (138.0 °C) and a 1 : 2 inter-molecular compound (IMC) (219.0 °C), which has a high dielectric constant (ε = 0.9 × 103) and electrical conductivity in the order ∼5 × 10−6 S m−1.

Synthesis, crystal growth and physicochemical studies on a novel organic inter-molecular compound; 3,5-dinitrobenzoic acid and salicylamide system

The phase diagram of salicylamide (SAM) and 3,5-dinitrobenzoic acid (DNBA) system was determined by the thaw-melt method. Results show the formation of an inter-molecular compound and two eutectics. The values of heat of mixing, entropy of fusion, roughness parameter, interfacial energy, and the excess thermodynamic functions were calculated from the enthalpy of fusion data determined by the differential scanning calorimetric (DSC) method. The spectroscopic investigations (IR and NMR) suggest the presence of hydrogen bonding between the components of the compound. A single crystal of the inter-molecular compound was grown using slow cooling technique from the mixed solvent of ethanol and triple distilled water in 2:1 volume ratio. The single crystal analysis and the atomic packing pattern of the grown crystal confirm the monoclinic crystal structure with P21/c space group. The solubility of the inter-molecular compound was determined in the mixed solvent at different temperatures. Using solubility and entropy of fusion data, the entropy of dissolution and heat of mixing were calculated. The optical transmittance spectra of the crystal of the inter-molecular compound show 75% transmittance and the band gap of the crystal was found to be 3.00eV. The refractive index of the crystal was computed to be 2.50 at the cut off wavelength.

Application of the PC-SAFT equation of state to modeling of solid-liquid equilibria in systems with organic components forming chemical compounds

Equilibrium diagrams of liquid and solid phases were calculated by the equation of state, based on the perturbed-chain statistical associating fluid theory (PC-SAFT) for binary and ternary systems constituted by associating substances (water, alcohols, amines, phenol, bisphenol A, acetamide). Phase diagrams were considered for systems in which congruently and incongruently melting intermolecular compounds are formed and for a system with limited mutual solubility of the components in the liquid state. The results of prognostication of phase equilibria were illustrated by the example of a ternary system constituted by bisphenol A, phenol, and water, in which an adduct of bisphenol A and phenol is formed.

Hydrothermal syntheses, crystal structures, and properties of two polyoxometalates [Cd(2,2′-bpy)3]2[PMoVMoVI 11O40] and [H3PMo12O40]·3(4,4′-bpy)·4H2O

Two Keggin-type phosphododecamolybdate compounds [Cd(2,2′-bpy)3]2[PMoVMoVI 11O40] (1) and [H3PMo12O40]·3(4,4′-bpy)·4H2O (2) (bpy=bipyridine) were prepared by the hydrothermal method for the first time and characterized by elemental analyses, X-ray single-crystal diffraction, ESR spectra, and IR spectra, showing that compound 1 consists of a mixed valence Keggin polyanion [PMoVMoVI 11O40]4− and two isolated coordinated cations [Cd(2,2′-bpy)3]2+, while compound 2 is an intermolecular compound based on organic substrate 4,4′-bpy and heteropoly acid unit H3PMo12O40. Furthermore, both the compounds show strong photoluminescence properties in the solid state at room temperature. The catalytic activities of the two compounds were also determined by the oxidation of benzaldehyde to benzoic acid using H2O2 as oxidant in a liquid–solid triphase system.